Method for collective production of magnetic heads having a bearing surface with specific height

ABSTRACT

Process for collective production of integrated magnetic heads with a supporting surface with a determined height. According to the invention the components of a board are thinned collectively be etching the board along area overlapping polar parts.

DESCRIPTION

1. Technical Field

The purpose of this invention is a process for collective production ofintegrated magnetic heads with a determined height of the supportingsurface.

Its applications are the production of helical recording heads on amagnetic tape, particularly for video recordings for the general publicand for professional applications (VCRs for the home, camescopes) andfor equipment used to save computer data on tapes or disks.

High frequencies made possible by the small size of heads integrated inthin layers enable digital recording (for example according to the DVCstandard for video, or the DDS standard for data processing). Computermass memories including tape data recorders have the highest storagecapacities and the lowest costs. Computer applications include dataarchiving systems, backups of hard disks for a system or a network forthe distribution of large software or data bases. VCR video recordingapplications could be extended to include applications for a videoserver on which several films are stored centrally.

2. State of Prior Art

FIGS. 1 to 3 attached illustrate the structure of a component for anintegrated magnetic head with thin layers according to document FR-A-2747 226. As illustrated in FIG. 1, the head comprises two polar parts 10₁, 10 ₂ separated by an airgap 14, two magnetic arms 16 ₁, 16 ₂ partlycovering the polar parts, and a magnetic flux closing part 18. All ofthese parts form a magnetic circuit. Conducting windings 20 ₁, 20 ₂, areplaced around the arms 16 ₁, 16 ₂, not shown, to read and/or write theinformation written and/or read on a recording support.

FIG. 2 shows the complete head with two conducting strips 22 ₁, 22 ₂used to access conducting windings 20 ₁, 20 ₂ and two electricalconnection pins 24 ₁, 24 ₂.

The head shown in FIGS. 1 and 2 may be made collectively usingtechniques taken from micro-electronics. The components can be separatedfrom each other by storing them in a matrix structure and then cuttingthem along straight lines, in order to obtain an individual magnetichead from a plate containing a number of components. A roundedsupporting surface necessary for correct operation of the head isobtained by machining the front part of the components of each headclose to polar parts 10 ₁, 10 ₂. In FIG. 2, the rounded profile is showndiagrammatically by line 26. This operation is carried out mechanicallyon each head.

FIG. 3 diagrammatically shows a longitudinal section along one of theconducting strips of a head and one of the arms of the magnetic circuit.It shows a substrate 30, for example made of silicon, with one of thepolar parts 10 ₁ or 10 ₂, a magnetic arm 16 ₁, or 16 ₂, a magneticclosing part 18, a conducting strip 22 ₁, or 22 ₂ and electricalconnection pins 24 ₁, 24 ₂. The assembly is covered by a superstrate 40,for example made of silicon. The supporting surface 26 near the front ofthe head has an appropriate rounded shape. Towards the back, thesuperstrate 40 is exposed to show the electrical connection pins 24 ₁,24 ₂.

The substrate—superstrate assembly may be thicker than the thicknessrequired for the supporting surface. For example, 500 μm thick siliconsubstrates and 300 to 500 μm superstrates are used frequently, althoughthe thickness of polar parts at the supporting surface must not exceedabout 300 μm. This is why the magnetic head is thinner at polar parts,as shown in FIG. 3, where it can be seen that the height h of thesupporting surface is less than the thickness of the assembly. Thismakes the contact between the head and the recording support moreintimate.

A helical recording head on a tape with a thickness of a few hundredmicrometers may be made thinner, for example to a value of between 40and 80 μm.

The head is thinned individually on each head, which is obviouslyexpensive. Furthermore, this operation is very difficult and couldirreparably damage the head, seriously reducing the productionefficiency.

The purpose of this invention is to correct these disadvantages.

DESCRIPTION OF THE INVENTION

Consequently, the invention suggests a process in which thinning is donecollectively and no longer individually. Therefore, the cost is lowerand the efficiency is better.

More precisely, the purpose of the invention is a process for thecollective production of integrated magnetic heads that consists ofmaking several components on a board, each with specific means capableof forming at least one magnetic head, these means comprising inparticular polar parts separated by an airgap, and separating thecomponents at the end of the process to obtain heads with an appropriateshaped supporting surface, this process being characterized in that thecomponents are collectively thinned by etching the board in a directionperpendicular to the plane of the board along areas overlapping thepolar parts, the individual heads thus obtained having a supportingsurface with a low determined height in the said direction.

The thinning operation may be done by photolithography or by mechanicaletching or by a combination of these two techniques.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1, already described, shows a magnetic head according to thecurrent practice;

FIG. 2, already described, shows a top view of a magnetic head with itselectrical connection pins;

FIG. 3, already described, shows a sectional view through the same head;

FIG. 4 shows a top view of a board with collective etching areas to bethinned;

FIG. 5 shows a perspective view of a board after partial etching;

FIG. 6 shows a more detailed view of the shape of heads with a thinnedsupporting surface;

FIG. 7 illustrates a manufacturing method with double photolithography;

FIG. 8 illustrates a manufacturing method with double mechanicaletching;

FIG. 9 illustrates a mixed manufacturing method, includingphotolithography and mechanical etching;

FIGS. 10A, 10B, 10C, 10D show four steps in a particular embodiment ofthe invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 4 shows a board 50 comprising components T. This board is obtainedby any known collective process and particularly by the processdescribed in document FR-A-2 747 226 mentioned above. These componentscontain each of the elements already shown in FIG. 2. According to theinvention, this board is etched in a direction perpendicular to itsplane, and polar parts of the various components overlap along the areasB. In this etching, the edge of the board is masked to leave an outerring 55 to maintain a certain stiffness of the board.

FIG. 5 shows a perspective view of the board 50 with etching close topolar parts in a manufacturing method in which the shape of thesupporting area 72 of the heads was also obtained collectively. ThisFIG. 5 also shows that the board may comprise a substrate 70, supportingthe components and a superstrate 80 covering them.

FIG. 6 shows the shape and thickness of the supporting surface and theconnection pins P in more detail.

As mentioned above, any type of etching may be used in order tocollectively thin the supporting surface. FIGS. 7 to 9 non-exhaustivelyshow three particular etching methods; FIG. 7 shows photolithography ofareas B in the superstrate and areas B′ in the substrate; FIG. 8 showsmechanical etching; FIG. 9 shows photolithography B of the superstrateand mechanical etching B′ of the substrate.

Mechanical photolithography may be done using a mask, the edges of whichdefine the width of the opening to be formed. The straightness and widthof the openings in the mask are not critical as they would be if theobjective were to define the supporting surface, since the onlyobjective is to make the board thinner.

Mechanical etching may consist of grooving formed using strips orgrinding wheels, for example diamond cutting wheels with controlleddepth. A single blade or a module containing several blades may be used(for example periodically spaced) in order to machine several modules atthe same time, thus increasing productivity. A programmable control isused to start and finish grooving by lowering and raising the bladesrespectively (along the direction perpendicular to the surface of theboard) without starting or stopping at the edge of the board, so that anungrooved area is left around the periphery of the board to improve theoverall stiffness.

The process that was described above may be used in combination withanother process described and claimed in a French patent applicationentitled “Process for the collective production of integrated magneticheads with a supporting surface obtained by photolithography” depositedby the applicant of this patent on the same day as the application forthis patent.

Photolithography operations designed to create the shape of thesupporting surface may be applied before or after thinning operations,or at the same time.

FIGS. 10A, 10B, 10C and 10D illustrate a process in which these twotechniques are combined.

The first thing that can be seen in FIG. 10A is a board 50 (typically300 μm thick) with a substrate 70, a superstrate 80 and components T.The first step is to etch the substrate to excavate first grooves 86 atleast partly overlapping polar parts. The depth “a” of the groove may beabout 105 μm and its width may be 200 μm This etching may be achieved bymechanical machining (for example using a saw) or by deep etching (forexample using plasma).

The next step is to deposit a double mask 82, 84 on the superstrate. Forexample, the mask 82 may be made of 0.5 μm of SiO₂, and the mask 84 maybe made of resin.

These masks are etched to form a common rounded edge above the polarparts to define the shape of the supporting surface, and a straight edgeabove the connections. The next step is etching through this doublemask, which consumes mask 82 completely (FIG. 10B). There is still partof the unetched superstrate on the area above the electricalconnections, but the area located in front of the polar parts is fullyetched along a surface 88 as far as the stop layer 75 which is the upperlayer of the substrate (for example made of SiO₂). This stop layer isthen etched in an appropriate reactor (for example RGV plasma).

After taking off the resin mask 84, a second groove 92 is formed in thesuperstrate (FIG. 10C) to start to thin the supporting surface. Thedepth “b” of this groove may be 55 μm and its width may be 100 μm fromthe edge 88. The objective is to thin the surface with a precision ofthe order of one micron.

Finally, (FIG. 10D), the board is mounted on a flexible adhesive film 94and the substrate is etched until it is perforated and enters groove 86.This etching gives an appropriate shaped supporting surface 96 to thepolar parts. The connection pins P are then cleared, for example by RIEetching. The depth of groove 92 is increased to give a groove 98 with adepth equal to “c”. The result is a supporting surface with height “h”,with two etchings 86 and 98 with depths “a” and “c”. For example, thedepths “a” and “c” may be of the order of 105 μm and the height “h” maybe of the order of 90 μm. It is easy to adapt depths “a” and “c”, toobtain the required height “h” and to center polar parts within thethickness of the supporting surface.

All that remains to be done is to separate the heads and to mount themon bases.

What is claimed is:
 1. A method process for collective production ofintegrated magnetic heads, the process comprising: making a plurality ofcomponents on a board, each component formed into a magnetic head havinga supporting surface and comprising first and second polar partsseparated by an air gap; etching the board in a direction perpendicularto a plane of the board so as to collectively thin the supportingsurface of each of the plurality of components at a location adjacentthe first and second polar parts to round the supporting surface foreach of the plurality of components; and separating the plurality ofcomponents to obtain individual magnetic heads, wherein the boardcomprises a substrate supporting the components and a superstratecovering said components, and in which the substrate and the superstrateare thinned by etching them to obtain supporting surfaces with a height.2. The process according to claim 1, in which the board is thinned byphotolithography.
 3. The process according to claim 1, in which theboard is thinned by mechanical etching.
 4. The process according toclaim 1, in which the board is thinned partly by photolithography andpartly by mechanical etching.
 5. The process according to claim 1, inwhich thinning does not affect a periphery of the board such that anouter ring disposed at the periphery of the board has originalthickness.
 6. The process according to claim 1, in which a first grooveis formed to at least partially overlap said first and second polarparts.
 7. The process according to claim 6, wherein the superstrate isetched through a double mask to define the shape of the supportingsurface close to the polar parts, a second groove is formed to thin thesuperstrate close to the polar parts, and the superstrate is etched infront of the polar parts to open up into the first groove.
 8. Theprocess according to claim 1, wherein the height of the supportingsurfaces is about 90 microns in said direction.
 9. A method forcollective production of integrated magnetic heads, the methodcomprising: making a plurality of components on a board, each componentformed into a magnetic head having a supporting surface and comprisingfirst and second polar parts separated by an air gap; etching the boardin a direction perpendicular to a plane of the board so as tocollectively thin a supporting surface of each of the plurality ofcomponents at a location adjacent the first and second polar parts toround the supporting surface, and wherein the height of the supportingsurface is less than the thickness of the board; and separating theplurality of components to obtain individual magnetic heads.
 10. Themethod according to claim 9, wherein the board is thinned byphotolithography.
 11. The method according to claim 9, wherein the boardis thinned by mechanical etching.
 12. The method according to claim 9,wherein the board is thinned by photolithography and by mechanicaletching.
 13. The method according to claim 9, wherein thinning does notaffect a periphery of the board such that an outer ring disposed at theperiphery of the board has original thickness.
 14. The method accordingto claim 9, wherein a first groove is formed to at least partiallyoverlap the first and second-polar parts.
 15. The method according toclaim 14, wherein the superstrate is etched through a double mask todefine the shape of the supporting surface close to the polar parts, asecond groove is formed to thin the superstrate close to the polarparts, and the superstrate is etched in front of the polar parts to openup into the first groove.
 16. The method according to claim 9, whereinthe height of the supporting surfaces is about 90 microns in thedirection.